He has just seen his old girlfriend for the first time in five years and he can't get his mind off of the situation that caused the loss of the use of his leg so he decides to use that in the teaching of the class.

The patients: "Three guys walk into a clinic."

"Person A, farmer, says he was fixing a fence. Tightness of the ankle, loss of muscle control."
The mis-diagnoses: snake bite
The final diagnosis: flesh eating disease caused by dog bite.

"And C, we've got Carmen Electra. Golfing." (Not the patient's real name but House uses her when visualizing a couple of these patients at different times.)
The mis-diagnoses: patient trying to score pain medication
The final diagnosis: "aneurysm that clotted, leading to an infarction" and muscle death

There are no other clinic patients

We learn that one of the stories is about the infarction which caused House's limp and chronic pain.

Possible ethical breach

Stacy waiting until House is in a coma and then giving the go-ahead for a middle ground he would have refused.

Extra diagnosis

House determines that the teacher who has been sick a lot, has gotten lead poisoning from his coffee cup.

Quotes / Scenes

House (after patient has a bad reaction to the anti-venom and they need to figure if this was for the right snake so reading the test on the snake they found): "Our guy got bit less than four hours ago. There's no way a snake regenerates that much venom that quickly."

Student #1: We're supposed to know how fast snakes make their venom?
House: "Nope. Unless you've got a patient who has been bit by one. Then it might be helpful. So what do we do now?"
Student #2: "He must have been bitten by a different snake. We go back and find it."
House: "Or you go online and find there's only three poisonous snakes in New Jersey: the copperhead, the timber rattler, and the coral. The copperhead and the timber rattler both respond to the antivenins we gave the guy."
Student #2: "So we give him the antivenin for the other one."
House: "Is that a question?"
Student #1: "Well, we can't just blindly give him another antivenin. Especially after the first one almost killed him. You said only three types of poisonous snakes commonly found in New Jersey. But what if this is an uncommon one?"
House: "Very good."
Student #1: "We've gotta find the right snake."
House: "No need. Odds are, by the time you get back the autopsy results will tell you what kind of snake it was."
House: "...Who gives the guy the other antivenin? And who goes looking for the snake?" (To each question, half the class raise their hands)
Student #3: "I assume that one choice kills him and one saves him."
House: "That's usually the way it works at the leg turning black stage."
Student #2: "So half of us killed him and half of us saved his life."
House: "Yeah."
Student #1: "But we can't be blamed for---"
House: "I'm sure this goes against everything you've been taught, but right and wrong do exist. Just because you don't know what the right answer is — maybe there's even no way you could know what the right answer is — doesn't make your answer right or even okay. It's much simpler than that. It's just plain wrong."

House: "How do they teach you how to tell someone that they're dying? It's kind of like teaching architects how to explain why their building fell down. Do you roleplay and stuff?"
Student #1: "Yeah, one of us gives the bad news and one of us gets the bad news."
House: "And what do you have to do to get an A in You're Dying 101? They grade you on gentleness and supportiveness? Is there a scale for measuring compassion? This buddy of mine, I gotta give him ten bucks every time somebody says 'Thank you'. Imagine that. This guy's so good, people thank him for telling them that they're dying.... I don't get thanked that often.... It's a basic truth of the human condition that everybody lies. The only variable is about what. The weird thing about telling someone they're dying is it tends to focus their priorities. You find out what matters to them. What they're willing to die for. What they're willing to lie for."

House (talking about himself and visions he had): "The patient was technically dead for over a minute...."
Wilson (from the back of the classroom): "Do you think he was dead? Do you think those experiences were real?"
House: "Define real. They were real experiences. What they meant, personally, I choose to believe that the white light people sometimes see, visions, this patient saw: they're all just chemical reactions that take place when the brain shuts down."
Foreman: "You choose to believe that?"
House: "There's no conclusive science. My choice has no practical relevance to my life, I choose the outcome I find more comforting."
Cameron: "You find it more comforting to believe that this is it?"
House: "I find it more comforting to believe that this isn't simply a test."